It depends on how long your cycle is. If you go 28 days from the first day of your last period to the first day of your next, than you have a 28 day cycle and it's easy to figure out. You ovulated and concieved 14 days after the day of your last period. For instance: the date of my last period was May 15th so I ovulated and concieved on the 29th. Unfortunetly, this still won't get you right on. Even if you have a perfect 28-day cycle like I do, some months you may ovulate a day or two off. Also, sperm can live up to five days in your body so even if you had s_x on say, the 3rd of the month, you may not get pregnant until the 5th when your egg shows up to be fertilized. The doctor usually just counts 280 days (40 wks) after the date of your last period to guess your due date. This may be altered later if you have an ultrasound before 12wks.
In other words, who actually knows the exact date you concieved.

I am a little confused on to when I concieved as well, my last period was on Sept 18th, we had relations on Sept 23 and 24th, and that was it, we did have relations on Oct 10th, but I found out I was pregnant on Oct 11th, so I know I concieved on Sept 23 or 24th, or could I have concieved before that????? I am confused but I wright everything down and keep track. So now I am so confused. Please help understand:)

I do not remember the last day of my period I know it was at the beginning of March. I found out I was pregnant on April 16 when I decided to go to the doctor and get checked because my period hadnt came. I had s_x with my man on march 23rd and they say by the ultrasound that my due date is 12/14/2004 can anyone help me please!

my daughter is Due on the 15th of April and I'm also confused as to when I conceived a little help would be nice... it appears no one actually knows how long you carry a child or when it's actually conceived.

i really do not remember when the day of my last period was ...my ultra sound says my due date is around the 8th of march but i was with two people, one on june 11th of 04 and other on june 18th of 04 and the doctor says i concieved in the middle of june...i also took a preganancy test on the 13th or 14th and it was negative it was too soon to tell but i am hoping that the day is the one that i was with on the 18th...please help who do you think it might be